custom listing code

i want to be able to modify how the custom fields will be displayed.

i’ve added the _item.php file to the child theme directory.

do i need to copy the whole code in ITEM_CONTENT function and paste in the _item.php file ???

when i have the file there in the directory in the admin under search results display in the CUSTOMIZE tab it says “The child theme selected has its own customized _item.php file therefore the options here are unavailable.”
should the same text be there for the listing page display CUSTOMIZE tab ???

just wanting to know is the code in ITEM_CONTENT function only used to replace things that are like [CUSTOMFIELD] in both the listing page and the search results page ???